- Fix 4G and 5G discrepancy in TLV padding requirements: 4G does not
need padding, whereas 5G needs, so make separate set of function for
padding for NR
- Fix packing/unpacking for (n)FAPI PARAM and CONFIG.request/response
messages
- Handle message padding to next 32-bit boundary, as per SCF
specification in packing and unpacking functions
- Account for message header size upon receiving message in PNF and VNF
This time constant plays a major role in how long a UE has to wait
maximally before it might be scheduled. For instance, if a UE had a lot
of traffic, the average traffic will be high, pushing the PF coefficient
down. If another UE with no traffic in the past becomes active with
heavy traffic, the first UE might not be scheduled for an extended
period of time.
In the AW2S-Amarisoft UE CI test pipeline, we sometimes see that the
maximum number of RLC retransmissions was reached. While this might not
be the (only) cause, scheduling a UE more often might prevent such
situations, and we saw an improved stability.
After removing RA.crnti, there is no need to use a separate function
nr_generate_Msg3_dcch_dtch_response() to generate Msg.4 (yes, the
function mentions Msg3 but it does Msg3 response == Msg.4).
Also, using nr_generate_Msg4() has the advantage that it waits until we
have the reconfiguration available in RLC to be sent to the UE. Finally,
we can delete the old nr_generate_Msg3_dcch_dtch_response() as we don't
need it anymore.
When t_poll_retransmit expires we need to consider an SDU for
retransmission.
We used to take the first SDU (which could be a segment, not a full SDU)
of the wait list and put it in the retransmit list.
When testing with some UE (Amarisoft UE) a bad behavior was detected.
This is what happens for the SDU with SN 6 (for illustration purpose).
The gNB is sending an SDU in several pieces (it is segmented).
slot n: rlc sn 6 [1 .. 119[ p=0 RECEIVED
slot n+x: rlc sn 6 ]120 .. 180[ p=0 RECEIVED
slot n+x+y: rlc sn 6 ]181 .. 210] p=1 not RECEIVED
Then when t_poll_retransmit expires rlc retransmits only the PDU of
slot n (with p=1 this time) and the UE replies with ack 6. So nothing
happens on the gnb side.
(We would have expected ack 7 + nack 6 181..end.)
Then after t_poll_retransmit expires again rlc retransmits only PDU
of slot n and the UE still replies with ack 6.
This goes on forever (or some other timeout occurs.)
The logic is now changed.
When t_poll_retransmit expires we transfer all the SDUs in the wait list
having the same SN as the head of the wait list into the retransmit list.
Testing with Amarisoft UE, it seems to work properly.
The RA.crnti field is marked as being used by NSA mode, but it is not.
OTOH, it is used in the case of RA with Msg.3 with C-RNTI MAC CE. The
latter does not necessarily need it, though, as we can change the RNTI
of the RA process when we receive C-RNTI MAC CE.
This introduces a slight complication, though, as we cannot remove the
MAC UE Context (generated when receiving Msg.3) directly when parsing
the C-RNTI MAC CE. Previously, we had both rnti and crnti in the RA
struct, and when sending Msg.4 after Msg.3 with C-RNTI MAC CE, we would
remove the UE context (this is changed in the next commit). Therefore,
we employ nr_mac_trigger_release_timer() which releases the UE after
60ms, circumventing this complication.
Robert Schmidt